1. Field of the Invention
The present invention generally relates to a numerically controlled machining apparatus such as, for example, a lathe, a planer, a drilling machine, a cutting machine and a milling machine, and, more particularly, to an interchangeable machine tool holder unit for use in such apparatus for the support of a rotary cutter which may be used for forming a precisely dimensioned bore or for forming an O-ring seat within the bore.
2. Prior Art
A machine tool holder unit includes a generally enlongated rotary body adapted to be interchangeably coupled to a machine spindle for rotation together therewith, the free end of which has a tool holder movable in a direction radially thereof. When in use, the tool holder is moved together with the rotary body during the rotation of the rotary body to allow a cutting element mounted in the vicinity of the tool holder to revolve about the longitudinal axis of the rotary body so that the tool holder can be moved in a direction radially of the rotary body. In the machine tool holder unit, the distance over which the tool holder is radially moved each time the rotary body undergoes a complete rotation about its longidutinal axis driven by the machine spindle is required to be very small, for example, one thousandth of a millimeter and, in addition, the tool holder unit itself must be of a precise design. Therefore, the tool holder unit must have a complicated mechanism built therein.
In view of the foregoing requirements to be fulfilled, a highly reliable, durable and precise tool holder unit has not yet been developed.